CVE-2008-5617 in rsyslog
Summary
by MITRE
The ACL handling in rsyslog 3.12.1 to 3.20.0, 4.1.0, and 4.1.1 does not follow $AllowedSender directive, which allows remote attackers to bypass intended access restrictions and spoof log messages or create a large number of spurious messages.
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Analysis
by VulDB Data Team • 05/29/2025
The vulnerability described in CVE-2008-5617 represents a critical access control flaw in rsyslog versions ranging from 3.12.1 through 3.20.0 and specifically affecting versions 4.1.0 and 4.1.1. This issue fundamentally undermines the security model of the logging daemon by allowing unauthorized entities to circumvent the intended access restrictions that should be enforced through the $AllowedSender directive. The flaw exists within the Access Control List handling mechanisms that are designed to control which sources can send log messages to the rsyslog server, creating a pathway for malicious actors to gain unauthorized access to the logging infrastructure.
The technical implementation of this vulnerability stems from improper validation of sender addresses within the rsyslog daemon's processing pipeline. When administrators configure the $AllowedSender directive, they expect that only specified sources will be permitted to transmit log data to the server. However, the flaw in the ACL handling logic means that this restriction is bypassed, allowing remote attackers to send log messages from unauthorized IP addresses or hostnames. This occurs because the system fails to properly enforce the access control rules that should be applied during message reception, creating a situation where the security boundaries are effectively nullified. The vulnerability manifests as a failure to perform proper authentication and authorization checks on incoming log messages, leading to a complete breakdown of the intended access control model.
The operational impact of this vulnerability extends far beyond simple unauthorized access to log data. Attackers exploiting this flaw can spoof legitimate log messages, potentially leading to confusion during security investigations and making it difficult to distinguish between genuine system events and maliciously crafted log entries. This capability enables adversaries to manipulate the audit trail that security professionals rely upon for detecting and responding to security incidents. Additionally, the vulnerability allows for the generation of large volumes of spurious messages, which can overwhelm the logging infrastructure and potentially impact system performance or availability. The ability to flood the system with unauthorized log entries also provides a means for conducting denial-of-service attacks against the logging services, while simultaneously obscuring legitimate security events through log message manipulation.
The vulnerability aligns with CWE-284, which addresses improper access control, and represents a classic example of how insufficient input validation and access control enforcement can lead to security breaches in network services. From an adversarial perspective, this flaw maps to several ATT&CK techniques including T1070.004 (Indicator Removal on Host - File Deletion) through the manipulation of log data, and T1562.001 (Impair Defenses - Disable or Modify Tools) by potentially disrupting logging capabilities. Organizations affected by this vulnerability should immediately implement mitigations including upgrading to patched versions of rsyslog, implementing additional network-level access controls, and monitoring for unusual log message patterns that might indicate exploitation attempts. The recommended remediation strategy involves not only patching the software but also reviewing and strengthening the overall logging security posture to prevent similar issues from occurring in other components of the security infrastructure.